14 . JOURNAL OF THE [January, 



face of which just one frustule could be made out. At a second 

 visit I found streaks in which the clay partook of the nature of a 

 richer clay, the frustules being easily seen because densely packed. 



" The interest in this deposit is somewhat intensified, as the 

 apocryphal ' Navicula craticula^ or ' Suriclla cra/iciila,' is quite 

 abundant therein, as may be noted on the slide. The other 

 former congeners, N'avicula cuspidata and Stauroieis phcemcente- 

 ron, form a majority, which characterizes the slide. Together 

 with these there are species, such as T. 7iiustca, Nitzschia circum 

 suta, Cymatopleura elUpiica, Navicula nobilis, JV. major., and a 

 number of other species, as mentioned in the list of San Pedro 

 Springs. Gen. J. D. (^ox has investigated the question of N. era- 

 ticula, and, I believe, regarded it at one time as possibly an in- 

 ternal plate or an integral part of JV. cuspidata, a matter which 

 also interested Dr. D. B. Ward in its solution. He communicated 

 to me, what he regarded as probable at the time, that he had 

 found JV. craticula in the Montgomery, Ala., fossil, fresh-water 

 earth, where he had not at the time been able to detect N. cuspi- 

 data. 



" Frustules of N. craticula occur on the Society's slide, having 

 one-eighth the length of N. cuspidata; and likewise frustules of 

 N. craticula as large as N. cuspidata. The N. cuspidata of this 

 deposit are relatively very large and strongly lined, and, side by 

 side with Stauroneis ph(Enicenteron, are very striking under study. 

 Duplicates of either of these slides, in the hands of expert system- 

 atists, would furnish data to extend present knowledge or clear 

 up disputed and doubtful points, as the case may be." 



The Corresponding Secretary also presented an additional 

 communication from Mr. Cunningham, accompanying a dona- 

 tion of packets of gravel, and dated Houston, Texas, October 

 14th, 1892, as follows: 



" A visitor at Houston, Texas, would be at once impressed by 

 the immense use made of a certain kind of coarse gravel as bal- 

 last for the various railroad tracks, and for surfacing the streets 

 of the city ; and, if he v/ere a mineralogist, he would at once 

 recognize the presence of petrified wood richly associated with 

 this gravel. In order to place them before the Society, I have 

 made a selection of about a dozen different specimen varieties of 

 these very highly silicified woods. The specimens present some- 



